The Flash season 4
Barry Allen and Iris West in The Flash TV show The CW

The Flash season 4 returns with a fun episode this Tuesday (7 November) at 8pm EST where Arrow's Felicity (played by actor Emily Bett Rickards) comes to Central City for Iris' bachelorette party and Caitlin Snow will fear that her Killer Frost past may come to haunt her.

Also, actress Katee Sackhoff is set to make her debut as Amunet Black, aka the boss of an underground black market for supervillains, in the fifth episode of season 4, which is titled, Girls Night Out.

The official synopsis reads as follows:

Having received an ominous threat from her old boss, Amunet (guest star Katee Sackhoff), Caitlin (Danielle Panabaker) fears that her past time as Killer Frost may be back to haunt her. Felicity (guest star Emily Bett Rickards) comes to Central City to help the girls celebrate Iris's (Candice Patton) bachelorette party, while Cisco (Carlos Valdes), Joe (Jesse L. Martin) and the guys take Barry out for a night on the town.

Executive producer Andrew Kreisberg spoke to TV Line about Sackhoff's debut and teased a "worst night ever" for Iris and Barry.

Kreisberg raved, "Katee is so amazing in the show. The performance that she has brought to the character is so beyond anything you'd expect from her.... She is most definitely not playing [Battlestar's] Starbuck."

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The EP also dished on the not so fun-filled outing for the gang, and revealed to the outlet, "I think it's the first episode we've ever done where Barry doesn't wear the suit."

"We started with the concept of, 'Wouldn't it be really funny if Barry goes for the bachelor party with the guys and Candice goes for a bachelorette party with the girls, and the guys end up having the worst night ever and the girls wind up saving the city?' That was where we started from, and that's where it ended up."Kreisberg added of this Tuesday's episode.

Click here to watch The Flash season 4 live via The CW app. You can also watch the episode online by clicking here (only in the US).